Chemical and sensory characterization of novel Sauvignon blanc alcoholic beverages infused with Chinese goji berries

Abstract

Lycium barbarum (goji berry) is a unique medicinal and edible plant from China. Chinese goji berry contains a variety of highly active nutrients, such as Lycium barbarum polysaccharides (LBPs), carotenoids, vitamins, thiamin, ascorbic acid, flavonoids, fatty acids, and phenolic acids. Both in vivo and in vitro pharmacological studies have shown that goji berry has antioxidant activity, and has an immune regulation effect on arteriosclerosis, neurodegeneration, diabetes and other age-related diseases. Due to the desirability of functional foods and beverages with health benefits to consumers, this research aims to develop a novel New Zealand goji berry fermented alcoholic beverage (FAB) using Marlborough Sauvignon Blanc and to develop winemaking strategies to prevent phenolic off-flavours (POFs) caused by volatile phenols produced by the yeast. Sensory evaluation results of a new goji FAB compared to goji wine and Sauvignon blanc wine showed that the most pronounced taste characteristics of the goji berry fermented wines were medicinal characters and associated bitterness. These unpleasant notes may be due to volatile phenols such as 4-vinyl guaiacol (4-VG) and 4-vinyl phenol (4-VP) produced by phenolic off-flavour + (POF+) Saccharomyces cerevisiae yeast strains, which can be further metabolized by Brettanomyces yeast spp. to produce further volatile phenols, such as 4-ethyl guaiacol (4-EG) and 4-ethyl phenol (4-EP). It has been suggested that the skins of goji berries harbour Brettanomyces spp. which may be the cause of the off-flavours in the new goji FAB. Therefore, volatile phenols were the focus of the study. Since hydroxycinnamic acids in goji berries are a precursor of volatile phenols, 4-VG and 4-VP showed significant differences in the three wines (P < 0.05). The results showed that the concentrations of 4-EP and 4-EG in goji berry fermented wine were much higher than those in Sauvignon blanc wine. Due to the higher concentrations of 4-EP and 4-EG, the off-flavor of Brettanomyces produced by fermentation with S. cerevisiae yeast on goji FAB was similar to that of S. cerevisiae. The content of precursors in goji berry and the number of microorganisms, such as Brettanomyces bruxellensis on the surface of goji berry. Microorganisms were able to convert p-coumaric acid and ferulic acid into 4-EP and 4-EG during fermentation, which explains the high content of 4-EP and 4-EG. The presence of Brettanomyces bruxellensis yeast, which produces these phenolic substances, on the skin of goji berries was investigated. However, none of the colonies isolated from dried goji berries were Brettanomyces spp. A second round of fermentation trials aimed to reduce the amounts of volatile phenols in the finished goji FAB using various winemaking strategies, including a POF- S. cerevisiae strain, V1116. Interestingly, DNA extraction taken from finished goji FAB wines did not yield Brettanomyces so the source of POF characters in these wines are still unknown. In order for Goji FAB to become a commercial mass-produced product and to be loved by consumers, so more research is required.